Astronomers at the University of California have discovered a new planet which is considered to be in the middle of the Habitable Zone of its parent star, a discovery which has raised the possibility of finding life on another planet.

Researchers found the planet while conducting the Lick-Carnegie exoplanet survey of Gliese 581, a red dwarf. The planet, named ' Gliese 581 g', is approximately 20 light years away from Earth and is hypothesised to have a generally rocky landscape with enough gravitational pull to accumulate an atmosphere.

Gliese 581g (whose first name is pronounced GLEE-za) circles a dim red star known as Gliese 581, once every 37 days, at a distance of about 14 million miles. That is smack in the middle of the so-called Goldilocks zone, where the heat from the star is neither too cold nor too hot for water to exist in liquid form on its surface.

Steven Vogt of the University of California stated that Gliese 581g potentially has a gravitational pull similar to that of Earth, which would allow humans to walk around upright on its surface although human inhabitation of the planet is in no foreseeable future. Vogt observed that there is a significant possibility that life exists on Gliese 581 g.

"Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 per cent," Vogt said. Only lichen, bacteria and other micro-organisms are expected to exist on the planet.

Gliese 581 g is thought to have a temperature range from extremely hot to freezing cold depending on the side with respect to its star. The average temperature is expected to range from −31 to −12 degrees Celsius.

But nobody really knows what is going on on Gliese 581g, said Sara Seager, a planetary astronomer at the Massachusetts Institute of Technology. “If it was all carbon dioxide, like Venus, it would be pretty hot,” she said, adding that she would give the planet a 90 percent chance of holding water.

That, she pointed out, is faint praise in scientific circles. “Sounds high, but would you fly on a plane that only had an 8 or 9 chance out of 10 of making it?” she asked.

“Everyone is so primed to say here’s the next place we’re going to find life,” Dr. Seager said, “but this isn’t a good planet for follow-up.”

Prior to this discovery, two other planets were discovered in the low or "cold" end and the high or "hot" end of the 'Habitable Zone', respectively, orbiting the same star.